Busbar and battery laminate

ABSTRACT

A battery module includes: a plurality of batteries stacked together; and a busbar that electrically connects the plurality of batteries with each other. The busbar has: a main body that extends along axis X along which the batteries are stacked together; and a plurality of connectors that protrude from the main body along an axis that intersects with the axis along which the batteries are stacked together, and are electrically connected with terminals of the batteries, respectively. The plurality of batteries are divided into a plurality of battery units. Each of the plurality of battery units includes at least two of the plurality of batteries. The busbar connects the at least two of the plurality of batteries of each of the battery units with each other in parallel. The busbar connects the battery units with each other in series.

CROSS-REFERENCE OF RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/639,084, filed on Feb. 13, 2020, which is the U.S. National Phaseunder 35 U.S.C. § 371 of International Patent Application No.PCT/JP2018/045028, filed on Dec. 7, 2018, which claims the benefit ofJapanese Patent Application No. 2017-243049, filed on Dec. 19, 2017, theentire disclosures of which Applications are incorporated by referenceherein.

TECHNICAL FIELD

The present invention relates to a busbar and a battery module.

BACKGROUND ART

A battery module is known as a battery used as a power source that needsto generate high voltage. The power source that needs to generate highvoltage is used for a vehicle, for example. The battery module includesa plurality of batteries electrically connected with each other. In sucha conventional battery module, terminals of batteries that are adjacentto each other are connected with each other by a busbar. For example,PTL 1 discloses a battery module. The battery module includes aplurality of batteries. Busbars connect the plurality of batteries witheach other in parallel to form a plurality of battery units. The busbarsconnect the battery units with each other in series. Such aconfiguration reduces a number of components, such as voltage detectionlines, and reduces cost of a battery device, compared with a case inwhich battery modules are connected with each other in parallel, andeach of the battery modules includes batteries connected with each otherin series by busbars.

CITATION LIST Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 2016-27578

SUMMARY OF THE INVENTION

The inventors of the present invention have earnestly studiedconfigurations that each connect batteries in parallel and series in abattery module. Consequently, the inventors of the present inventionhave recognized following problems. That is to say, since batteries areconnected with each other in parallel, electric current that flowsthrough busbars increases. Therefore, power of heating generated by thebusbars increases. Especially in recent years, battery modules need toproduce high power and deal with rapid charging. Consequently, electriccurrent that flows through busbars is further increasing. Consequently,power of heating generated by busbars is increasing. If power of heatinggenerated by busbars increases, heat may be transferred from the busbarsto batteries. Consequently, temperatures of the batteries may rise.Consequently, the batteries may less efficiently generate electricity.

The present invention is made in view of the above situation. It is anobject of the present invention to provide a technique that allows heatgenerated by busbars to have a weaker influence on batteries.

An aspect of the present invention is a battery module. The batterymodule includes: a plurality of batteries stacked together; and a busbarthat electrically connects the plurality of batteries with each other.The busbar has: a main body that extends along an axis along which thebatteries are stacked together; and a plurality of connectors thatprotrude from the main body along an axis that intersects with the axisalong which the batteries are stacked together, and are electricallyconnected with terminals of the batteries, respectively. The pluralityof batteries are divided into a plurality of battery units. Each of theplurality of battery units includes at least two of the plurality ofbatteries. The busbar connects the at least two of the plurality ofbatteries of each of the battery units with each other in parallel. Thebusbar connects the battery units with each other in series.

Another aspect of the present invention is a busbar. The busbarelectrically connects a plurality of batteries stacked together witheach other. The busbar has: a main body that extends along an axis alongwhich the batteries are stacked together; and a plurality of connectorsthat protrude from the main body along an axis that intersects with theaxis along which the batteries are stacked together, and areelectrically connected with terminals of the batteries, respectively.

Any combination of the above components is also an effective aspect ofthe present invention. Further, the present invention is expressed informs of methods, devices, and systems. The methods, devices, andsystems are also effective aspects of the present invention.

The present invention allows heat generated by the busbar to have aweaker influence on batteries.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view that illustrates a configurationof a battery module according to a first exemplary embodiment.

FIG. 2 is an enlarged perspective view that illustrates one of busbarsin the battery module.

FIG. 3 is an enlarged perspective view that illustrates one of busbarsin a battery module according to a second exemplary embodiment.

FIG. 4 is a schematic perspective view that illustrates a configurationof one of busbars of a battery module according to an example ofvariations.

FIG. 5 is an enlarged schematic plan view that illustrates one ofbusbars in a battery module according to a third exemplary embodiment.

FIG. 6 is an enlarged schematic plan view that illustrates one ofbusbars in a battery module according to a fourth exemplary embodiment.

FIG. 7 is an enlarged perspective view that illustrates one of busbarsin a battery module according to a fifth exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described based on preferredexemplary embodiments with reference to the drawings. The exemplaryembodiments are exemplifications and do not limit the invention. Allfeatures described in the exemplary embodiments and combinations of thefeatures are not necessarily essential to the invention. The samereference marks are assigned to the same or equivalent components,members, and processes illustrated in the drawings. Explanation for thesame or equivalent components, members, and processes will not berepeated as appropriate. For convenience, scales or shapes of portionsillustrated in the drawings are determined to facilitate explanation ofthe portions. The scales or shapes of the portions should not beinterpreted as limitation unless otherwise mentioned. Further, somecomponents may be illustrated on slightly different scales in differentdrawings. Further, if terms “first”, “second”, and the like are used inthe present description or claims, the terms “first”, “second”, and thelike do not mean any order or importance, but are used to distinguishbetween one configuration and another configuration unless otherwisementioned.

First Exemplary Embodiment

FIG. 1 is a schematic perspective view that illustrates a configurationof a battery module according to a first exemplary embodiment. Batterymodule (=battery stack) 1 (1A) includes a plurality of busbars 2, and aplurality of batteries 4 electrically connected with each other bybusbars 2.

For example, each of batteries 4 is a rechargeable secondary battery,such as a lithium-ion battery, a nickel-metal hydride battery, or anickel-cadmium battery. Each of batteries 4 is what is called aprismatic (=rectangular) battery. Each of batteries 4 has an exteriorcan that has a shape like a flat rectangular prism. One side of theexterior can has a substantially rectangular opening that is notillustrated. Electrodes and electrolyte are inserted into the exteriorcan through the opening. Sealing sheet 6 is attached to the opening ofthe exterior can. Sealing sheet 6 seals the exterior can. Positiveterminal 8 protrudes from one of two lengthways ends of sealing sheet 6.Negative terminal 8 protrudes from the other lengthways end of sealingsheet 6. Hereinafter, positive terminal 8 is referred to as positiveterminal 8 a, as appropriate. Further, negative terminal 8 is referredto as negative terminal 8 b, as appropriate. If polarity of terminals 8does not need to be distinguished, positive terminals 8 a and negativeterminals 8 b are collectively referred to as terminals 8.

Terminals 8 protrude from respective openings of sealing sheet 6. Agasket as a seal is disposed between a periphery of each of terminals 8and the opening of sealing sheet 6. The gasket tightly fills a gapbetween sealing sheet 6 and terminal 8. Further, the gasket does notallow a short circuit between sealing sheet 6 and terminal 8. Theexterior can, sealing sheet 6, and terminals 8 are electricalconductors, and are made of metal, for example. The gasket is aninsulator and is made of resin, for example. Sealing sheet 6 includes asafety valve (not illustrated) between the pair of terminals 8. If apressure rises to or above a predetermined value in the exterior can,the safety valve opens to release gas in the exterior can.

In the present exemplary embodiment, a top of battery 4 includes sealingsheet 6, and a bottom of battery 4 is opposite the top of battery 4.Further, battery 4 has two main sides that each connect the top ofbattery 4 with the bottom of battery 4. Of six sides of battery 4, themain sides each have the largest area. In addition to the top, thebottom, and the two main sides, battery 4 has two sides. The tops ofbatteries 4 constitute a top of battery module 1. The bottoms ofbatteries 4 constitute a bottom of battery module 1. The sides ofbatteries 4 constitute sides of battery module 1. For convenience,assume that the top of battery module 1 is a vertically upper side ofbattery module 1, and the bottom of battery module 1 is a verticallylower side of battery module 1.

The plurality of batteries 4 are stacked together at predeterminedintervals. Main sides of batteries 4 that are adjacent to each other arein contact with each other. The terms “stacked together” mean that aplurality of components are arranged along any one axis. Therefore,stacking batteries 4 together may mean horizontally arranging theplurality of batteries 4. Further, batteries 4 are arranged in such amanner that terminals 8 face in a same direction. For convenience,terminals 8 face upward along vertical axis Z (an axis indicated byarrow Z in FIG. 1 ).

Each of busbars 2 is an elongated metal component. The plurality ofbatteries 4 are stacked together, and electrically connected with eachother by busbars 2. Busbars 2 are made of a metal, such as copper oraluminum. For example, busbars 2 are welded to terminals 8 of batteries4. A configuration of busbars 2 will be described later. Further, itwill be described later how busbars 2 connect batteries 4 with eachother.

Battery module 1 includes a plurality of separators not illustrated. Theseparators are also referred to as insulating spacers. The separatorsare made of a resin that has an insulation property, for example. Forexample, the separators are made of a thermoplastic resin, such aspolypropylene (PP), polybutylene terephthalate (PBT), a polycarbonate(PC), NORYL (registered trademark) resin (modified polyphenylene ether(PPE)). The separators are arranged between batteries 4, and arearranged between battery 4 and each of end plates 10, respectively. Endplates 10 will be described later. Consequently, exterior cans ofbatteries 4 that are adjacent to each other are insulated from eachother. Further, the exterior cans of batteries 4 are insulated from endplates 10.

Battery module 1 also includes the pair of end plates 10. End plates 10are each made of a metal sheet, for example. The plurality of batteries4 and the plurality of separators that have been stacked together aredisposed between the pair of end plates 10. The pair of end plates 10are each disposed along axis X along which batteries 4 are stackedtogether (an axis indicated by arrow X in FIG. 1 ). The pair of endplates 10 are adjacent to outermost batteries 4, respectively. However,the separator is between each of the pair of end plates 10 and outermostbattery 4. Outermost busbars 2 along axis X along which batteries 4 arestacked together function as terminals connectable with othercomponents.

Battery module 1 also includes a pair of binding components 12. The pairof binding components 12 bind batteries 4, the separators, and endplates 10 that have been stacked together. The pair of bindingcomponents 12 are also referred to as binding bars. The pair of bindingcomponents 12 are each disposed along horizontal axis Y (an axisindicated by arrow Y in FIG. 1 ) that is perpendicular to axis X alongwhich the plurality of batteries 4 are stacked together. Alonghorizontal axis Y, terminals 8 are arranged in each of batteries 4. Eachof binding components 12 has flat portion 12 a and bent portions 12 b.Flat portion 12 a is rectangular and is parallel to sides of batteries4. Bent portions 12 b protrude from ends of sides of flat portion 12 a,respectively, toward batteries 4. For example, each of bindingcomponents 12 is a rectangular metal sheet whose sides are bent.

Two bent portions 12 b that are opposite each other along axis X alongwhich batteries 4 are stacked together are fixed to the pair of endplates 10, respectively, with screws, for example. Consequently, thepair of end plates 10 and the pair of binding components 12 bind theplurality of batteries 4 and the plurality of separators together.Binding components 12 bind the plurality of batteries 4 along axis Xalong which batteries 4 are stacked together. Consequently, bindingcomponents 12 position the plurality of batteries 4 along axis X alongwhich batteries 4 are stacked together. Further, bottoms of theplurality of batteries 4 are in contact with lower bent portions 12 b ofbinding components 12. However, separators are disposed between thebottoms of the plurality of batteries 4 and lower bent portions 12 b ofbinding components 12. Tops of the plurality of batteries 4 are incontact with upper bent portions 12 b of binding components 12. However,separators are disposed between the tops of the plurality of batteries 4and upper bent portions 12 b of binding components 12. Consequently, theplurality of batteries 4 are vertically positioned. Then busbars 2 areelectrically connected with terminals 8 of batteries 4. Consequently,battery module 1 is made.

Next, a configuration of busbars 2 according to the present exemplaryembodiment will be described in detail. Further, it will be described indetail how busbars 2 electrically connect batteries 4 with each other.FIG. 2 is an enlarged perspective view that illustrates one of thebusbars in the battery module. Each of busbars 2 has main body 16 and aplurality of connectors 18. Main body 16 is elongated and extends alongaxis X along which batteries 4 are stacked together. The plurality ofconnectors 18 are electrically connected with terminals 8 of batteries4, respectively. Connectors 18 are arranged at predetermined intervalsalong an axis along which main body 16 extends (axis X along whichbatteries 4 are stacked together). Connectors 18 protrude from main body16 along an axis that intersects with axis X along which batteries 4 arestacked together (horizontal axis Y). Therefore, busbar 2 has a shapelike a comb.

In the present exemplary embodiment, main body 16 of busbar 2 is closerto centers of batteries 4 along horizontal axis Y than terminals 8 are.Further, connectors 18 of busbar 2 protrude toward sides of batteries 4.That is to say, main body 16 is apart from terminals 8 of batteries 4.Main body 16 may be closer to sides of batteries 4 along horizontal axisY than terminals 8 are.

The plurality of batteries 4 are divided into a plurality of batteryunits 20. Each of the plurality of battery units 20 includes at leasttwo batteries 4. Busbars 2 connect batteries 4 of each of battery units20 with each other in parallel. Further, busbars 2 connect battery units20 with each other in series. In an example illustrated in FIG. 2 ,first battery unit 20 a includes first battery 4 a and second battery 4b that are stacked together in such a manner that positive terminal 8 aof first battery 4 a is adjacent to positive terminal 8 a of secondbattery 4 b, and negative terminal 8 b of first battery 4 a is adjacentto negative terminal 8 b of second battery 4 b. Similarly, secondbattery unit 20 b includes first battery 4 a and second battery 4 b thatare stacked together in such a manner that positive terminal 8 a offirst battery 4 a is adjacent to positive terminal 8 a of second battery4 b, and negative terminal 8 b of first battery 4 a is adjacent tonegative terminal 8 b of second battery 4 b.

First battery unit 20 a and second battery unit 20 b are stackedtogether in such a manner that positive terminal 8 a of first batteryunit 20 a is adjacent to negative terminal 8 b of second battery unit 20b. Second battery 4 b of each of battery units 20 is closer to the otherbattery unit 20 than first battery 4 a of each of battery units 20 is.Connectors 18 of busbar 2 are connected with terminals 8, respectively.Consequently, busbar 2 connects first battery 4 a and second battery 4 bof each of battery units 20 with each other in parallel. Further, busbar2 connects first battery unit 20 a with second battery unit 20 b inseries.

The plurality of connectors 18 include first connectors 18 a and secondconnectors 18 b. First connector 18 a is connected with first battery 4a of first battery unit 20 a. First battery 4 a of first battery unit 20a is apart from second battery unit 20 b. Further, second connector 18 bis connected with second battery 4 b of first battery unit 20 a. Secondbattery 4 b of first battery unit 20 a is adjacent to second batteryunit 20 b. First connection point A1 is a connection point where firstconnector 18 a is connected with first battery 4 a. Second connectionpoint A2 is a connection point where second connector 18 b is connectedwith second battery 4 b. Third connection point B is a connection pointwhere second connector 18 b is connected with main body 16. Firstconnector 18 a and second connector 18 b do not have a same shape, buthave different shapes. Consequently, a difference in electricalresistance between a path from first connection point A1 to thirdconnection point B and a path from second connection point A2 to thirdconnection point B is reduced. Busbar 2 is similarly connected withbatteries 4 of second battery unit 20 b.

In the present exemplary embodiment, an area of a cross section of firstconnector 18 a is different from an area of a cross section of secondconnector 18 b. More specifically, a width (a dimension along axis Xalong which batteries 4 are stacked together) of second connector 18 bis smaller than a width (a dimension along axis X along which batteries4 are stacked together) of first connector 18 a. A thickness (adimension along vertical axis Z) of second connector 18 b is equal to athickness (a dimension along vertical axis Z) of first connector 18 a.Consequently, area C2 of a cross section of second connector 18 b alongaxis X along which batteries 4 are stacked together is smaller than areaC1 of a cross section of first connector 18 a along axis X along whichbatteries 4 are stacked together.

Area C1 of a cross section of first connector 18 a along axis X alongwhich batteries 4 are stacked together is smaller than area C3 of across section of main body 16 along an axis (horizontal axis Y) thatintersects with axis X along which batteries 4 are stacked together.Further, area C2 of a cross section of second connector 18 b along axisX along which batteries 4 are stacked together is smaller than area C3of a cross section of main body 16 along an axis (horizontal axis Y)that intersects with axis X along which batteries 4 are stackedtogether. Busbar 2 has a section that connects battery units 20 witheach other in series. Busbar 2 also has a section that connectsbatteries 4 with each other in parallel. Busbar 2 has a shape thatallows the section of busbar 2 that connects battery units 20 with eachother in series to have electrical resistance that is lower thanelectrical resistance of the section of busbar 2 that connects batteries4 with each other in parallel.

The section of busbar 2 that connects battery units 20 with each otherin series is a section of main body 16. The section of main body 16 isbetween two second connectors 18 b. More specifically, the section ofbusbar 2 that connects battery units 20 with each other in series is asection between two third connection points B. One of two thirdconnection points B is a point where one of two second connectors 18 bis connected with main body 16. The other one of two third connectionpoints B is a point where the other one of two second connectors 18 b isconnected with main body 16. The section of busbar 2 that connectsbatteries 4 with each other in parallel includes first connector 18 aand second connector 18 b that correspond to each of battery units 20.The section of busbar 2 that connects batteries 4 with each other inparallel also includes main body 16, but does not include a section ofmain body 16 that is between two third connection points B. Whole mainbody 16 has a uniform width and a uniform thickness. Area C1 of a crosssection of first connector 18 a is smaller than area C3 of a crosssection of main body 16. Area C2 of a cross section of second connector18 b is smaller than area C3 of a cross section of main body 16. Thesection of busbar 2 that connects batteries 4 with each other inparallel includes connectors 18. However, the section of busbar 2 thatconnects battery units 20 with each other in series does not includeconnectors 18. Therefore, the section of busbar 2 that connects batteryunits 20 with each other in series has electrical resistance that islower than electrical resistance of the section of busbar 2 thatconnects batteries 4 with each other in parallel.

As described above, battery module 1 according to the present exemplaryembodiment includes the plurality of batteries 4, and busbars 2 thatelectrically connect the plurality of batteries 4 with each other. Eachof busbars 2 has main body 16 that extends along axis X along whichbatteries 4 are stacked together. Each of busbars 2 also has theplurality of connectors 18 that are electrically connected withterminals 8 of batteries 4, respectively. A direction in which each ofconnectors 18 protrudes from main body 16 intersects with axis X alongwhich batteries 4 are stacked together. Further, each of connectors 18protrudes from main body 16 along XY plane. Ends of connectors 18 areconnected with terminals 8, respectively. Consequently, main body 16 isnot vertically over terminals 8.

The plurality of batteries 4 are divided into the plurality of batteryunits 20. Each of the plurality of battery units 20 includes at leasttwo batteries 4. Busbars 2 connect batteries 4 of each of battery units20 with each other in parallel. Busbars 2 connect battery units 20 witheach other in series. Consequently, total electric current of batteries4 connected with each other in parallel flows through part of main body16. Power J of heating generated by busbar 2 is a value that is aproduct of a square of electric current I that flows through busbar 2and resistance R of busbar 2 (J=I²R). Each of connectors 18 generatespower of heating (I²R). Further, a section of main body 16 whereelectric current from one of batteries 4 flows generates power ofheating (I²R). Further, a section of main body 16 where total electriccurrent from batteries 4 connected with each other in parallel flowsgenerates power of heating that is a product of I²R and a square of anumber of batteries 4 connected with each other in parallel. In case ofthe present exemplary embodiment, a section of main body 16 where totalelectric current from batteries 4 connected with each other in parallelflows generates power of heating that is 4×I²R since two batteries 4 areconnected with each other in parallel. Therefore, a temperature of mainbody 16 may significantly increase, and thus may have an influence onbatteries 4.

To deal with the problem, each of busbars 2 has main body 16 that isparallel to axis X along which batteries 4 are stacked together, andconnectors 18 that is parallel to horizontal axis Y. Connectors 18 areconnected with terminals 8, respectively. Therefore, main body 16 thatgenerates much power of heating is apart from terminals 8. Consequently,heat generated by busbars 2 has a weaker influence on batteries 4.Consequently, heat of busbars 2 less increases temperatures of batteries4. Consequently, batteries 4 efficiently generate electricity. Further,since temperatures of batteries 4 are less increased, larger electriccurrent is allowed to flow through busbars 2.

The gaskets disposed between terminals 8 and sealing sheets 6 areespecially relatively easily affected by heat. Therefore, it isimportant to allow temperatures of terminals 8 to be less increased byheat of busbars 2. Busbars 2 according to the present exemplaryembodiment allow temperature of terminals 8 to be less increased.Consequently, the gaskets do not melt. Consequently, each of the gasketstightly seals between terminal 8 and sealing sheet 6.

The plurality of connectors 18 include first connectors 18 a and secondconnectors 18 b. The plurality of battery units 20 include first batteryunit 20 a and second battery unit 20 b that are connected with eachother in series by busbars 2. First battery unit 20 a includes firstbattery 4 a connected with first connector 18 a, and second battery 4 bconnected with second connector 18 b. Second battery 4 b is closer tosecond battery unit 20 b than first battery 4 a is. Since second battery4 b is closer to second battery unit 20 b than first battery 4 a is, apath through which electricity flows from second battery 4 b to secondbattery unit 20 b is shorter than a path through which electricity flowsfrom first battery 4 a to second battery unit 20 b. Therefore, if firstconnector 18 a and second connector 18 b had a same shape, the two pathsthrough which electricity flows would have different electricalresistance. Consequently, first battery 4 a and second battery 4 b wouldnot be uniformly consumed.

First connector 18 a and second connector 18 b have respectiveparticular shapes. The respective particular shapes reduce a differencein electrical resistance between a path from first connection point A1where first connector 18 a is connected with battery 4 to thirdconnection point B where second connector 18 b is connected with mainbody 16 and a path from second connection point A2 where secondconnector 18 b is connected with battery 4 to third connection point Bwhere second connector 18 b is connected with main body 16. In thepresent exemplary embodiment, an area of a cross section of firstconnector 18 a is different from an area of a cross section of secondconnector 18 b. Consequently, a difference in electrical resistancebetween the paths through which electricity flows is reduced. Morespecifically, an area of a cross section of second connector 18 b issmaller than an area of a cross section of first connector 18 a.Consequently, the shorter path through which electricity flows includessecond connector 18 b whose electrical resistance is increased.Consequently, a difference in electrical resistance between the pathsthrough which electricity flows is reduced. Consequently, batteries 4are more uniformly consumed.

Area C1 of a cross section of first connector 18 a along axis X alongwhich batteries 4 are stacked together is smaller than area C3 of across section of main body 16 along an axis that intersects with axis Xalong which batteries 4 are stacked together. Further, area C2 of across section of second connector 18 b along axis X along whichbatteries 4 are stacked together is smaller than area C3 of a crosssection of main body 16 along an axis that intersects with axis X alongwhich batteries 4 are stacked together. Consequently, heat that has beengenerated by main body 16 is less transferred to batteries 4 throughconnectors 18. Further, the section of busbar 2 that connects batteryunits 20 with each other in series has electrical resistance that islower than electrical resistance of the section of busbar 2 thatconnects batteries 4 with each other in parallel. Consequently, thesection of busbar 2 that connects battery units 20 with each other inseries generates less heat.

Second Exemplary Embodiment

A battery module according to a second exemplary embodiment and thebattery module according to the first exemplary embodiment have a sameconfiguration except for a difference in configuration betweenrespective busbars. Hereinafter, a difference in configuration betweenthe battery module according to the present exemplary embodiment and thebattery module according to the first exemplary embodiment will bemainly described. A same configuration will be simply described, or willnot be described.

FIG. 3 is an enlarged perspective view that illustrates one of busbarsin the battery module according to the second exemplary embodiment. Inthe present exemplary embodiment, battery module 1 (1B) includes busbars2. Each of busbars 2 has main body 16 and a plurality of connectors 18.Main body 16 extends along axis X along which batteries 4 are stackedtogether. The plurality of connectors 18 are electrically connected withterminals 8 of batteries 4, respectively. Connectors 18 are arranged atpredetermined intervals along an axis along which main body 16 extends(axis X along which batteries 4 are stacked together). Connectors 18protrude from main body 16 along an axis that intersects with axis Xalong which batteries 4 are stacked together (horizontal axis Y).

Battery module 1 includes first battery unit 20 a and second batteryunit 20 b. First battery unit 20 a includes first battery 4 a and secondbattery 4 b that are stacked together. Second battery unit 20 b includesfirst battery 4 a and second battery 4 b that are stacked together.Busbar 2 connects first battery 4 a and second battery 4 b of each ofbattery units 20 with each other in parallel. Further, busbar 2 connectsfirst battery unit 20 a with second battery unit 20 b in series.

The plurality of connectors 18 include first connectors 18 a and secondconnectors 18 b. First connector 18 a is connected with first battery 4a of first battery unit 20 a. First battery 4 a of first battery unit 20a is apart from second battery unit 20 b. Further, second connector 18 bis connected with second battery 4 b of first battery unit 20 a. Secondbattery 4 b of first battery unit 20 a is adjacent to second batteryunit 20 b. First connector 18 a and second connector 18 b do not have asame shape, but have different shapes. Consequently, a difference inelectrical resistance between a path from first connection point A1 tothird connection point B and a path from second connection point A2 tothird connection point B is reduced. Busbar 2 is similarly connectedwith batteries 4 of second battery unit 20 b.

In the present exemplary embodiment, an area of a cross section of firstconnector 18 a is different from an area of a cross section of secondconnector 18 b. More specifically, a thickness (a dimension alongvertical axis Z) of second connector 18 b is smaller than a thickness (adimension along vertical axis Z) of first connector 18 a. Consequently,an area of a cross section of second connector 18 b is smaller than anarea of a cross section of first connector 18 a. Further, main body 16has thick portions 16 a and thin portion 16 b. Thick portions 16 a areconnected with first connectors 18 a, respectively. Thick portions 16 ahave a thickness that is equal to a thickness of first connectors 18 a.Thin portion 16 b is connected with second connectors 18 b. Thin portion16 b has a thickness that is equal to a thickness of second connectors18 b.

Heat generated by busbars 2 of battery module 1 according to the presentexemplary embodiment has a weaker influence on batteries 4. Further,each of busbars 2 of battery module 1 according to the present exemplaryembodiment reduces a difference in electrical resistance between a paththrough which electricity flows from first battery 4 a to second batteryunit 20 b and a path through which electricity flows from second battery4 b to second battery unit 20 b. Consequently, batteries 4 are moreuniformly consumed.

Hereinafter, an example of variations on battery module 1 according tothe second exemplary embodiment will be described. FIG. 4 is a schematicperspective view that illustrates a configuration of one of busbars of abattery module according to the example of variations. Busbar 2 ofbattery module 1 according to the present example of variations includesfirst sheet 22 and second sheets 24. First sheet 22 and each of secondsheets 24 are stacked together. In a plan view, first sheet 22 has ashape that corresponds to whole main body 16 and whole connectors 18. Ina plan view, each of second sheets 24 has a shape that corresponds tothick portion 16 a and first connector 18 a. Consequently, a thicknessof first connectors 18 a is different from a thickness of secondconnectors 18 b. Further, a thickness of thick portions 16 a isdifferent from a thickness of thin portion 16 b. The present example ofvariations has an effect that is similar to an effect of a thirdexemplary embodiment. Further, since the sheets are stacked together,busbar 2 that has different thicknesses is more easily made.

Third Exemplary Embodiment

A battery module according to a third exemplary embodiment and thebattery module according to the first exemplary embodiment have a sameconfiguration except for a difference in configuration betweenrespective busbars. Hereinafter, a difference in configuration betweenthe battery module according to the present exemplary embodiment and thebattery module according to the first exemplary embodiment will bemainly described. A same configuration will be simply described, or willnot be described.

FIG. 5 is an enlarged schematic plan view that illustrates one ofbusbars in the battery module according to the third exemplaryembodiment. In the present exemplary embodiment, busbar 2 of batterymodule 1 (1C) has main body 16 and a plurality of connectors 18. Mainbody 16 extends along axis X along which batteries 4 are stackedtogether. The plurality of connectors 18 are electrically connected withterminals 8 of batteries 4, respectively. Connectors 18 are arranged atpredetermined intervals along an axis along which main body 16 extends(axis X along which batteries 4 are stacked together). Connectors 18protrude from main body 16 along an axis that intersects with axis Xalong which batteries 4 are stacked together (horizontal axis Y).

Battery module 1 includes first battery unit 20 a and second batteryunit 20 b. First battery unit 20 a includes first battery 4 a and secondbattery 4 b that are stacked together. Second battery unit 20 b includesfirst battery 4 a and second battery 4 b that are stacked together.Busbar 2 connects first battery 4 a and second battery 4 b of each ofbattery units 20 with each other in parallel. in series.

The plurality of connectors 18 include first connectors 18 a and secondconnectors 18 b. First connector 18 a is connected with first battery 4a of first battery unit 20 a. First battery 4 a of first battery unit 20a is apart from second battery unit 20 b. Further, second connector 18 bis connected with second battery 4 b of first battery unit 20 a. Secondbattery 4 b of first battery unit 20 a is adjacent to second batteryunit 20 b. First connector 18 a and second connector 18 b do not have asame shape, but have different shapes. Consequently, a difference inelectrical resistance between a path from first connection point A1 tothird connection point B and a path from second connection point A2 tothird connection point B is reduced. Busbar 2 is similarly connectedwith batteries 4 of second battery unit 20 b.

In the present exemplary embodiment, first connector 18 a and secondconnector 18 b each have a shape like a crank, and each have two bends.First connector 18 a has an end connected with terminal 8, extends fromthe end along horizontal axis Y, has a 90° bend, extends from the 90°bend toward second battery 4 b, and extends along horizontal axis Y, andis connected with main body 16. Second connector 18 b has an endconnected with terminal 8, extends from the end along horizontal axis Y,has a 90° bend, extends from the 90° bend toward first battery 4 a, andextends along horizontal axis Y, and is connected with main body 16.That is to say, first connector 18 a and second connector 18 b form ashape that has line symmetry. An axis of the line symmetry is line M.Line M passes through third connection point B and is parallel tohorizontal axis Y. In other words, an end of first connector 18 a isconnected with an end of second connector 18 b. The connected ends offirst connector 18 a and second connector 18 b are connected with mainbody 16.

Consequently, a length from first connection point A1 to thirdconnection point B is equal to a length from second connection point A2to third connection point B. An area of a cross section of firstconnector 18 a is equal to an area of a cross section of secondconnector 18 b. Consequently, electrical resistance of first connector18 a from first connection point A1 to third connection point B is equalto electrical resistance of second connector 18 b from second connectionpoint A2 to third connection point B.

Heat generated by busbars 2 of battery module 1 according to the presentexemplary embodiment has a weaker influence on batteries 4. Further,each of busbars 2 of battery module 1 according to the present exemplaryembodiment reduces a difference in electrical resistance between a paththrough which electricity flows from first battery 4 a to second batteryunit 20 b and a path through which electricity flows from second battery4 b to second battery unit 20 b. Consequently, batteries 4 are moreuniformly consumed.

Fourth Exemplary Embodiment

A battery module according to a fourth exemplary embodiment and thebattery module according to the first or third exemplary embodiment havea same configuration except that the battery module according to thefourth exemplary embodiment includes busbars that each have a shape of acombination of the busbar according to the first exemplary embodimentand the busbar according to the third exemplary embodiment. Hereinafter,a difference in configuration between the battery module according tothe present exemplary embodiment and the battery module according to thefirst exemplary embodiment will be mainly described. A sameconfiguration will be simply described, or will not be described.

FIG. 6 is an enlarged schematic plan view that illustrates one ofbusbars in the battery module according to the fourth exemplaryembodiment. In the present exemplary embodiment, busbar 2 of batterymodule 1 (1D) has main body 16 and a plurality of connectors 18. Mainbody 16 extends along axis X along which batteries 4 are stackedtogether. The plurality of connectors 18 are electrically connected withterminals 8 of batteries 4, respectively. Connectors 18 are arranged atpredetermined intervals along an axis along which main body 16 extends(axis X along which batteries 4 are stacked together). Connectors 18protrude from main body 16 along an axis that intersects with axis Xalong which batteries 4 are stacked together (horizontal axis Y).

Battery module 1 includes first battery unit 20 a and second batteryunit 20 b. First battery unit 20 a includes first battery 4 a, secondbattery 4 b, third battery 4 c, and fourth battery 4 d that are stackedtogether. Second battery unit 20 b includes first battery 4 a, secondbattery 4 b, third battery 4 c, and fourth battery 4 d that are stackedtogether. Busbar 2 connects first to fourth batteries 4 a to 4 d of eachof battery units 20 with each other in parallel. Further, busbar 2connects first battery unit 20 a with second battery unit 20 b inseries.

The plurality of connectors 18 include first connectors 18 a, secondconnectors 18 b, third connectors 18 c, and fourth connectors 18 d.First connector 18 a is connected with first battery 4 a of firstbattery unit 20 a. In first battery unit 20 a, first battery 4 a is themost apart from second battery unit 20 b. Second connector 18 b isconnected with second battery 4 b of first battery unit 20 a. In firstbattery unit 20 a, second battery 4 b is adjacent to first battery 4 a.Third connector 18 c is connected with third battery 4 c of firstbattery unit 20 a. In first battery unit 20 a, third battery 4 c isadjacent to second battery 4 b. Fourth connector 18 d is connected withfourth battery 4 d of first battery unit 20 a. In first battery unit 20a, fourth battery 4 d is the closest to second battery unit 20 b. Firstto fourth connectors 18 a to 18 d do not have a same shape, but havedifferent shapes. Consequently, differences in electrical resistancebetween a path from first connection point A1 where first connector 18 ais connected with terminal 8 to third connection point B, a path fromsecond connection point A2 where second connector 18 b is connected withterminal 8 to third connection point B, a path from third connectionpoint A3 where third connector 18 c is connected with terminal 8 tothird connection point B, and a path from fourth connection point A4where fourth connector 18 d is connected with terminal 8 to thirdconnection point B are reduced. Busbar 2 is similarly connected withbatteries 4 of second battery unit 20 b.

In the present exemplary embodiment, an area of a cross section of firstconnector 18 a, an area of a cross section of second connector 18 b, andan area of a cross section of third connector 18 c are different fromeach other. More specifically, a width of second connector 18 b issmaller than a width of first connector 18 a. Further, a width of thirdconnector 18 c is smaller than a width of second connector 18 b.Further, a width of fourth connector 18 d is equal to a width of thirdconnector 18 c. Further, fourth connector 18 d has a shape like a crank,and has two bends. Consequently, fourth connector 18 d is longer thanthird connector 18 c.

That is to say, an area of a cross section of third connector 18 c issmaller than an area of a cross section of second connector 18 b.Further, an area of a cross section of second connector 18 b is smallerthan an area of a cross section of first connector 18 a. Consequently,differences in electrical resistance between a path through whichelectricity flows from first connection point A1 where first connector18 a is connected with first battery 4 a to third connection point B, apath through which electricity flows from second connection point A2where second connector 18 b is connected with second battery 4 b tothird connection point B, and a path through which electricity flowsfrom third connection point A3 where third connector 18 c is connectedwith third battery 4 c to third connection point B are reduced. Further,fourth connector 18 d is longer than third connector 18 c. Consequently,differences in electrical resistance between a path through whichelectricity flows from fourth connection point A4 where fourth connector18 d is connected with fourth battery 4 d to third connection point B,the path through which electricity flows from first connection point A1to third connection point B, the path through which electricity flowsfrom second connection point A2 to third connection point B, and thepath through which electricity flows from third connection point A3 tothird connection point B are reduced.

Heat generated by busbars 2 of battery module 1 according to the presentexemplary embodiment has a weaker influence on batteries 4. Further,differences in electrical resistance between a path through whichelectricity flows from first battery 4 a to second battery unit 20 b, apath through which electricity flows from second battery 4 b to secondbattery unit 20 b, a path through which electricity flows from thirdbattery 4 c to second battery unit 20 b, a path through whichelectricity flows from fourth battery 4 d to second battery unit 20 bare reduced. Consequently, batteries 4 are more uniformly consumed.

Fifth Exemplary Embodiment

A battery module according to a fifth exemplary embodiment and thebattery module according to the first exemplary embodiment have a sameconfiguration except for a difference in configuration betweenrespective busbars. Hereinafter, a difference in configuration betweenthe battery module according to the present exemplary embodiment and thebattery module according to the first exemplary embodiment will bemainly described. A same configuration will be simply described, or willnot be described.

FIG. 7 is an enlarged perspective view that illustrates one of busbarsin the battery module according to the fifth exemplary embodiment. Inthe present exemplary embodiment, busbar 2 of battery module 1 (1E) hasmain body 16 and a plurality of connectors 18. Main body 16 extendsalong axis X along which batteries 4 are stacked together. The pluralityof connectors 18 are electrically connected with terminals 8 ofbatteries 4, respectively. Connectors 18 are arranged at predeterminedintervals along an axis along which main body 16 extends (axis X alongwhich batteries 4 are stacked together). Connectors 18 protrude frommain body 16 along an axis that intersects with axis X along whichbatteries 4 are stacked together (horizontal axis Y).

Battery module 1 includes first battery unit 20 a and second batteryunit 20 b. First battery unit 20 a includes first battery 4 a and secondbattery 4 b that are stacked together. Second battery unit 20 b includesfirst battery 4 a and second battery 4 b that are stacked together.Busbar 2 connects first battery 4 a and second battery 4 b of each ofbattery units 20 with each other in parallel. in series.

Busbar 2 has displacement allowing portions 28 that allow relativedisplacement (=deviation, or movement) of batteries 4. Batteries 4 areelectrically connected with each other by busbar 2. Part of each ofdisplacement allowing portions 28 extends toward battery 4, or in adirection where a distance between battery 4 and displacement allowingportion 28 becomes close or apart. In the present exemplary embodiment,bases of connectors 18 are displacement allowing portions 28. The basesof connectors 18 are connected with main body 16. Displacement allowingportions 28 extend in a direction that intersects with XY plane.Displacement allowing portions 28 are made by bending the bases ofconnectors 18. In the present exemplary embodiment, a width ofdisplacement allowing portions 28 is equal to a width of connectors 18.However, a width of displacement allowing portions 28 is not necessarilyequal to a width of connectors 18. A position of main body 16 andpositions of connectors 18 are different from each other along verticalaxis Z. Displacement allowing portions 28 allow or absorb mainlydisplacement (=deviation, or movement) of batteries 4 along horizontalaxis Y, and allow mainly dimensional variation in batteries 4 alonghorizontal axis Y.

Main body 16 also has displacement allowing portions 28 that extend in adirection that intersects with XY plane. Displacement allowing portions28 of main body 16 are arranged along axis X along which batteries 4 arestacked together. Displacement allowing portions 28 of main body 16 arearranged between connectors 18. In the present exemplary embodiment,main body 16 is U-shaped and protrudes along vertical axis Z.Displacement allowing portions 28 of main body 16 are made by bendingmain body 16. In the present exemplary embodiment, a width (a dimensionalong horizontal axis Y) of displacement allowing portions 28 is equalto a width of main body 16. However, a width of displacement allowingportions 28 is not necessarily equal to a width of main body 16.Displacement allowing portions 28 of main body 16 allow mainly movementof batteries 4 along axis X along which batteries 4 are stackedtogether, and allow mainly dimensional variation in batteries 4 alongaxis X along which batteries 4 are stacked together. Displacement(=deviation, or movement) of batteries 4 along vertical axis Z anddimensional variation in batteries 4 along vertical axis Z are mainlyallowed by variation in inclination of connectors 18, but may be allowedby displacement allowing portions 28.

Heat generated by busbars 2 of battery module 1 according to the presentexemplary embodiment has a weaker influence on batteries 4. Further,busbars 2 are more securely connected with batteries 4. Consequently,the plurality of batteries 4 are more securely connected with eachother. Further, in the present exemplary embodiment, areas of crosssections of connectors 18 may be different from each other, or lengthsof connectors 18 may be different from each other. Consequently,differences in electrical resistance between paths through whichelectricity flows from batteries 4 may be reduced.

The present invention is not limited to the above exemplary embodiments.Some of the exemplary embodiments may be combined together.Alternatively, the exemplary embodiments may be modified based onknowledge of the person of ordinary skill in the art. For example,designs of the exemplary embodiments may be variously modified. If someof the exemplary embodiments are combined together, a resultantexemplary embodiment falls within the scope of the present invention.Further, if the exemplary embodiments are modified, resultant exemplaryembodiments also fall within the scope of the present invention. If someof the exemplary embodiments are combined together, a resultantexemplary embodiment has effects of the exemplary embodiments that havebeen combined together. Further, if the exemplary embodiments aremodified, resultant exemplary embodiments each have an additional effectof the modification.

In the above exemplary embodiments, batteries 4 are prismatic batteries.However, a shape of batteries 4 is not particularly limited and may becylindrical, for example. Further, a total number of batteries 4 ofbattery module 1 is not particularly limited. A total number of batteryunits 20 of battery module 1 is not particularly limited. A number ofbatteries 4 of each of battery units 20 is not particularly limited.Further, exterior cans of batteries 4 may be each covered with aninsulating sheet, such as a heat shrink tube.

1. A battery module comprising; a plurality of batteries stackedtogether along a first direction, wherein each of the plurality ofbatteries includes a first terminal and a second terminal which arealigned along a second direction perpendicular to the first direction;and a busbar that electrically connects the plurality of batteries witheach other, wherein the busbar has; a main body that extends along thestacked direction; and a connector that protrudes from the main bodyalong the second direction, and are electrically connected withterminals of the batteries, respectively, the plurality of batteries aredivided into a plurality of battery units, each of the plurality ofbattery units including at least two of the plurality of batteries, thebusbar connects the at least two of the plurality of batteries of eachof the battery units with each other in parallel, the busbar connectsthe battery units with each other in series, an upper surface of themain body includes a first region and a second region, which arearranged along the first direction and connect the at least two of theplurality of batteries of one of the plurality of batteries in parallel,the first region and the second region are arranged in parallel withconnection portions of corresponding batteries to which the first regionand the second region are connected along the second direction, thefirst region is disposed closer to the battery units than the secondregion in a third direction perpendicular to the first direction and thesecond direction, the second region is disposed at an end portion of themain body along the first direction.
 2. The battery module according toclaim 1, wherein an area of a cross section of the connector along thefirst direction is smaller than an area of a cross section of the mainbody along the second direction.
 3. The battery module according toclaim 1, wherein the connector includes a first connector and a secondconnector, the plurality of battery units include a first battery unitand a second battery unit that are connected with each other in seriesby the busbar, the first battery unit includes a first battery connectedwith the first connector, and a second battery connected with the secondconnector, the second battery is closer to the second battery unit thanthe first battery is, and the first connector and the second connectordo not have a same shape, but have different shapes, and a difference inelectrical resistance between a path from a connection point where thefirst connector is connected with the first battery to a connectionpoint where the second connector is connected with the main body, and apath from a connection point where the second connector is connectedwith the second battery to the connection point where the secondconnector is connected with the main body, is reduced.
 4. The batterymodule according to claim 3, wherein an area of a cross section of thefirst connector is different from an area of a cross section of thesecond connector.
 5. The battery module according to claim 1, whereinthe busbar has a displacement allowing portion that allow relativemovement of the batteries electrically connected with each other by thebusbar.
 6. The battery module according to claim 5, wherein part of thedisplacement allowing portion extends in a direction where a distancebetween the batteries and the displacement allowing portion becomesclose or apart.
 7. The battery module according to claim 1, wherein thebusbar has a shape that allows a section of the busbar that connects thebattery units with each other in series to have electrical resistancethat is lower than electrical resistance of a section of the busbar thatconnects the batteries with each other in parallel.
 8. The batterymodule according to claim 1, wherein a part of the body that constitutesthe second region has lower electrical resistance than a part thatconstitutes the first region.